BackgroundPrevention offers an effective public health strategy for cancer control. One approach that could be incorporated within general practice is the provision of personalised risk information. Few trial data are available concerning the impact of cancer risk information on behaviour.AimTo assess the short-term effects on computed cancer risk and self-reported health-related behaviours of providing personalised cancer risk information.MethodA total of 1018 participants, recruited through the online platform Prolific, were randomised to either a control group receiving cancer-specific lifestyle advice alone or one of three intervention groups receiving the same lifestyle advice alongside their estimated 10-year risk of developing one of the five most common preventable cancers. Cancer risk was calculated from self-reported behavioural risk factors and presented in one of three formats: bar-chart, pictograph, or qualitative scale. The primary outcome was change from baseline in computed risk relative to an individual with a recommended lifestyle (RRI) at 3 months. Secondary outcomes included: self-reported health-related behaviours, accuracy of risk perception, risk conviction, anxiety, worry, intention to change behaviour, self-efficacy, and response-efficacy.ResultsAt immediate follow-up, accuracy of risk perception (P<0.001), risk conviction (P <0.001), and response-efficacy (P = 0.04) increased in all intervention groups. After 3 months there were no between-group differences in change in RRI (P = 0.68) or any of the secondary outcomes.ConclusionThis study has shown that a risk communication intervention can increase short-term risk accuracy and response efficacy and for the first time that risk conviction can be manipulated through risk communication. However, these effects were not sustained over time or associated with behaviour change.